Add test-suite
Bump Cabal-version to 1.10

Cabal-version >= 1.10 is required to run the test-suite.
acme-omitted.cabal: add homepage and source-repository
Differentiate the merely omitted from the truly undefined

Note that these definitions require the use of Control.Exception,
which means no more Haskell98 compatibility.
Rewrite module description

Take into account new developments
Acme.Omitted: rewrite module documentation
Merge branch 'isOmitted'
Merge branch 'new-docs'
Test the behaviour of isOmitted and isUndefined
Bump base depend for test suite